Effect of Heat Input on Microstructure and Mechanical Properties of Inconel-718 EB Welds

In this paper effect of electron beam welding heat input on the microstructure and mechanical properties of Inconel 718 was studied. Sheet of 2 mm thickness was used with an average grain size of 30 μm. Five different heat inputs ranging from 36 J/mm to 180 J/mm were used to make full penetration welds. Welding current was varied from 18 mA to 90 mA and other welding parameters were kept constant. Change in heat input altered the geometry of the weld (width to depth ratio) and the microstructure of fusion zone (FZ) and heat affected zone (HAZ) also changed. As the heat input increased the interdentric spacing in FZ was increased from 3.5 μm to 6 μm. Grain boundary liquation was found in all the welds. Intensity of liquation increased with decrease in heat input and the microfissuring was observed only in the lowest heat input weld. Change in heat input did not significantly affect the tensile properties of the weld.